Forward,backward, up, Down... four directions.
It's the same 4 directions as shiho giri as David explained, but NOT as he explained in terms of 4 different attackers.
Essentially, you can throw (the same) uke in the opposite direction of the attack, i.e. behind him, in the same direction as the attack, or to either side of the attack (from the same side that you are on).
In actuality, it can be in *any* direction... probably easier to show than explain in writing...